Phase-converter exciting system



R. E. HELLMUND.

PHASE CONVERTER EXCITING SYSTEM, APPLICATION FILED AUG-7,1916.

4 SHEETS-SHEET I.

WITNESSES INVENTOR Rudolf E f/el/mund "ATTORNEY Patented May 3, 1921.

R. E. HE'LLMUND.

PHASE CONVERTER EXCITING SYSTEM;

APPLICATION FILED AUGJ, 1916.

1,376,429. Patented May 3,1921..

4 SHEETSSHEET 2.

000"! I! II a WITNESSES: INVENTOR 22 4 23M; film/f 5 m/mwyd a! aAT/TORNEY R. E. HELLMUND.

PHASE CONVERTER EXCITING SYSTEM.

APPLICATION FILED AUG-7,1916.

1,376,429. nte May 3,1921.

, 4 SHEET$SHEET 3.

WITNESSES: INVENTOR K E M. Z M a /f [flu/W0 R. E. HELLMUND.

PHASECONVERTER EXCITING SYSTEM.

APPLICATION FILED AUG-7.1916.

Patented May 3, 1921.

4 SHEETSSHEET 4.

I INVENTOR fiz/aa/f [T Hal/mafia A TToRNEY unmunno uu m moun-QM-0900000oomoooaoaoo-oo-oo WITNESSES UNITED srATEsP TsnT Fries.

RUDOLF E. HELLMUND, 0F Sl/VISSVALE, PENNSYLVANIA, ASSIGNOR TO WESTING-HOUSE ELECTRIC AND I'IHTNUFAGTUBING CQMPANY, A CORPORATION OF PENN-SYLVANIA.

PHASE-CONVERTER EXCITING i SYSTEM.

To all to 7mm it may concern:

Be it known that I, RUnoLr E. HELLMUND, a subject of the Emperor ofGermany, and a resident of Swissvale, in the county of Alle gheny andState of Pennsylvania, have iii-- of the T-connected, rotary type,together with auxiliary automatic compounding and phase-correctingapparatus; Figs. 2 to 6, inclusive, and Figs. 8 to 13, inclusive, arediagrammatic views of modifications of the system shown in 1; and Fig. 7is a sequence chart setting forth the order 01": switch manipulation inthe system of Fig. 6 for the operation thereof in accordance with myinvention. 1

In the operation of phase-converters, such, for example, as thoseemployed for deriving three-phase currents ;trom a single-phase sourceor for balancing unbalanced polyphase systems, it is well known factthat, with an increase of load, there is a tendency for the secondaryinduced voltage to fall off because of the drops in the stator and rotorcircuits. This is an undesirable condition as promotes unbalancing inthe polyphase distributing system, with resultant unsatisfactoryoperation of polyphase apparatus connected thereto. In my copendingappliation, Serial No. 108,567, tiled July 11, 1916, I set forth meanswhereby an extraneous voltage is introduced into the rotor circuits forforcing the load current therethrough as by a suitable synchronousbooster. By suitable adjustment or" sail a xiliary voltage, the dropacross the rotary terminals may be suitably compensated for and I may,in fact, by a further increase in said auxiliary voltage, compensate forthe voltage drops in the primary winding itself and in associatedapparatus.

t has been found that the load currents in the rotor circuits of aphase-converter are Specification of Zetters Patent.

Patented May 3, 1921.

Serial No. 113,454.

of twice the frequency of the supply circuit and it is'thereforenecessary that the abovementioned, auxiliary, compensating volta e be ofdouble frequency in order to properly perform its function.

In the present invention, I provide means whereby direct-current,exciting apparatus is combined with said compounding exciting means sothat automatic control of the power-factor of the phaseconverter and ofassociated apparatus may be obtained.

Referring to Fig. 1. of the drawin tor a more detailed understanding ofmy invention, I show a phase-converter of the rotary type at 1 1, saidphase converter comprising a primary stator winding 15, a secondarystator winding 16 and a rotor 17 provided.

with a three-phase winding 18. The windings 15 and 16 are joined to formthe ordi nary T-connection, as is well known in the art. The outerterminals of the rotor winding 18 are connected, through suitable sliprings 19 and through the field windings 20-20 of a polyphase commutatormachine 21, to the brushes of said machine. The rotor of he machine 21is mounted on the shaft of the phase-converter 14 or otherwisemechanically coupled thereto so as to be driven thereby. -The fieldwindings 2020 are circumferentially displaced, with respect to theirassociated brushes, so that they combine the effects of exciting andinducing windings. There is generated in the rotor of the machine 21,therefore, double-frequency currents of such amount and phase as toproperly compound the machine A, compensating not only for ohmic butalso for reactive dr ps therein, all as explained in detail in mystore-mentioned application. An additional machine Q2. of the commutatertype is also mounted upon the shaft of the phase converter 17 andcomprisesan armature23, an exciting field winding 24 and ashort-'circuited neutralizing or compensating field winding 25. Theexciting winding 24 may be energized from any suitable direct-currentsource, such, for example, as a battery 26, through an adjustableresistor 27. The armature of the machine 22 is connected in circuitbetween one ofthe phases ofthe winding 18 and the machine 21.

With the connections as described, direct current is produced in themachine 22 and flows through the appropriate phases of the winding 18,causing the rotor 17 of the phase converter 14 to lock into synchronismand to thereafter run synchronously. By suitable adjustment of theresistor 27, the corresponding unidirectional field in the rotor 17 maybe adjusted in strength, with corresponding adjustment ofthe powerfactor of the phase converter 14, as is well known in connection withthe ordinary synchronous condenser.

An important function of the neutralizing winding 25 in the operation ofthe machine 22 is the elimination of the alternating cross-field whichis set up therein by the fiow of a portion of the load current of therotor 17 therethrough.

. It isunnecessary to employ two distinct machines on the shaft of thephase-converter, as the functions of a direct-current exciter and ofv analternating-current exciter may be combined in a single machine. Asystem of this character is shown in Fig. 2 wherein, so far as possible,like parts to those employed in the system of Fig. 1 are denoted bylike. reference numerals. The composite exciting machine is shown at 28and includes a rotor 29 of such length that its windings may be underthe influence of 'two stators, one of which carries the alternating-current field windings 20-20 and the other of which carries theunidirectional current field windings 24 and 25. The machine 29 is shownas driven by a direct-current motor 30, rather than being attached tothe shaft of the phase-converter, but, ohviously, either ofthese methodsof driving may be employed, as is found most convenient.

The machine 23 is shown greatly exaggerated in dimensions, with respectto the phase-converter 14, for the sake of clearness but it will beunderstood that, in practice, said two machines bear substantially thesame ratio to each other in size that is borne by the ordinary generatorand its exciter.

I may go still further in simplifying the exciting means for aphase-converter by placing all the field windings therefor on a singlestator, as indicated in Fig. 3. The composite exciter machine is shownat 31 and need be provided with but a single pair of brushes, as it isnecessary to bring out but one phase from the polyphase rotor winding 18of the phase-converter 14. The double-frequency alternating excitationof the machine 31 is provided by a single set of field windings 20, anda unidirectional current component of the excitation is provided by afield winding 24, as before. The field windings 20 and 24 should bemounted on separate polar projections,'and each polar projectioncarrying a portion of the unidirectional current winding 24 should beprovided with a short-circuited field winding 25 in order to preventalternating flux from threading the 001124.

Another system embodying a composite exciter is shown in Fi 4. Thecomposite exciter 31 is of the polyphase commutator type and is providedwith three exciting field windings 2020, operating as in Fig. 1. Afourth field winding 32 is mounted substantially in line with one of thefield wind ings 20 and is excited by direct-current from a generator 33driven by a repulsion motor 34. The circuit joining the generator 33 andthe field winding 32 includes the secondary winding 35 of a transformer36, the primary winding 37 of which is in series with the field winding20 that is coaxial with the field windin 32. With these connections, thealternating current of the winding 20'induces an alternatingelectromotive force in the field winding 32 but the secondary winding 35is so connected that the electromotive force of the transformer 36 isequal thereto and opposite in its effects. By this means, the harmfuleffect of the alternating fiux threading the field winding 32 ininducing an alternatin -current voltage in the unidirectional excitingcircuit and producing resultant disturbance by superimposingalternatingwaves upon the unidirectional exciting currentis removed.

The exciter machme 31 is driven by a commutator motor 38, said motorcomprising a g short-circuited armature 39, an exciting field winding 40and an inducing field winding 41. The exciting field. winding 40 isconnected across the supply transformer, and the field 41 is energized,in accordance with the load current of the phase-converter 14, through asuitable current transformer 42. Thus, the speed of the motor 38 varieswith the load, which provides additional means for in creasing both thedirect-current and the alternating-current excitation with the converterload, with resultant possibility of increased compensating'andcompounding effects. The motor 34, driving the generator 33, isenergized in accordance with the voltage of the secondary winding 16 ofthe phase-converter 14.

A still further consolidation and simplification of my system may beeffected, as shown in Fig. 5, by combining the windings 20 and 32 ofFig. 4 into single winding 43 traversed by both the alternating and theunidirectional exciting currents. The transformer 36 operates as in thesystem of Fig. 4, eliminating the effect of the alternating fiux uponthe unidirectional exciting current.

7 A certain compounding effect may be obtained, in a system of thecharacter described, by placing the neutralizing field winding in serieswith the armature, designing it for slight over-compensation and then byshifting the armature brushes slightly away from the axis thereof. A

system of. this character is shown in Fig' 6 wherein an exciting machine31 is provided with a single pair of brushes for connection in a singlephase of the rotor winding of the phase-converter 14, and furthercomprises an exciting winding 44, a neutralizing winding and anadditional field winding 46 in alinement with the winding 44.

The various elements of the system may be interconnected by suitableswitches 47 to 54, inclusive. The winding 44 is connected to beenergized from a direct-current source 26 which, in addition, supplies adriving motor 30 for the exciting apparatus. For starting, the switches49 and 51 are closed, as indicated in Fig. -7, whereby the armature oftlie machine 31, the exciting field winding 46 and the neutralizingfield wind ing 45 are all connected to the source in series with theprimary winding of the phase converter. After the phase-converter hasbeen started and brought up to substantially synchronous speed, thearmature of the exciter 31 and the neutralizing field winding 45 areconnected in series with the rotor winding of the phase-converter byclosing switches 47, 48, 50, 52 and 53 and opening the switches 49 and51, all as indicated in the chart of Fig. 7. Under these conditions, thefield winding 44 supplies unidirectional excitation, and the fieldwinding 46 is short circuited by the closure of the switch 53 to act asa damping winding and restrain alternating flux from traversing thewinding 44. The field winding 45 serves as a compensating Winding and,in addition, supplies a small alternating-current field by reason of thebrush displacement, said field inducing the desired alternatingelectromotive force for compounding.

In the system of Fig. 8, the exciter machine 31 is provided with aunidirectionalcurrent exciting winding 44, with an alternatingcurrentexciting winding 46 in alinement therewith and with a short-circuitedneutralizing winding 54 in line with the brushes. The winding 44 isenergized from the source 26, and a transformer 36 interlinks the supplycircuit thereof with the circuit of the phase-converter for theneutralization of the alternating electromotive force induced therein.At the outset,

the switches 58 and 59 are closed and, for

subsequent operation, said switches are opened and the remainingswitches closed. Thus, the winding 44 supplies a unidirectional fieldduring normal operation and the Winding 46' furnishes an alternatingfield both during starting and subsequent operation.

In my aforementioned application, a system is disclosed in which thearmature of the exciting machine is short circuited through the brushesand the load currents of the phase-converter traverse only the fieldwindings of the exciter machine. In this manner, commutation troublesare avoided. Fig. 9 shows a system of this character wherein means areprovided, in addition, for supplying a unidirectional exciting current.The exciter machine 31 is shown as of the polyphase commutator type, thefield windings 20-20 thereof being connected in star to the rotorwinding 18 of the phase-converter 14 and the commutator including three,equally-spaced brushes 61 which are connected together. Aunidirectional-current source 62 is inserted in one of the main leads tothe rotor 17, as in the system of Fig. 1. The exciter machine 31 isshown arranged to be driven from the car axle 63, ifthe system in question is to be applied to a railway vehicle,

thus illustrating another variation of my invention.

As pointed out in my aforementioned ap plication, it may, in certaininstances, be undesirable to have the exciter machine derive itsexciting current from the hase-converter because of the harmful e set onthe phase-converter power-factor. It was accordingly proposed to renderthe exciter machine self-exciting, particular attention beingdirectedto' the desirable characteristics of the lVinter-Eichberggenerator when used inv this connection. A system of this character isshown in Fig. 10 wherein the exciter machine 31 is provided with aunidirectional-current field winding 24 and with a short-circuitedneutralizing or compensating winding 25 in line therewith. The armatureof the machine 31 is provided with two sets of brushes 64'64 and 6565having a quadratureirelation' to each other. The brushes 64-64, inquadrature to the exciting field winding 24, are connected in a phase ofthe rotor winding 18 of the phase converter 14. The brushes 65-65, inline with the exciting field winding 24', are connected together throughthe primary winding 35 of a transformer 36, the secondary winding ofwhich is inserted in series with the brushes 64-64. By this arrangement,both alternating and direct-current excitation are derived from themachine 31, as will appear from the following consideration.Double-frequency rotor current from the machine 14 flows through thebrushes 64-64 and establishes an alternating-field having a horizontalaxis through the armature of the machine 31. Said alternating fieldproduces a rotational, alternating electromotive force between thebrushes 65-65, and said electromotive force is introduced into theconverter rotor circuit by the transformer 36. The field winding 24,which is excited by direct current from the battery 26, produces avertical field through the armature of the machine 31, which,'in turn,

produces a rotational unidirectional electromotive force between thebrushes (i l-64 to produce a flow of direct exciting current through thewinding 18 The alternating field established in line with the brushes65-65 by the fiow of alternating current therethrough may be damped outeither by a superimposed electromotive' force in the direct-currentexciting circuit or by the inducing winding 25. The rotor current of theconverter now has a direct-current component which establishes aunidirectional field in line with the brushes 64- -64, in ducing, inturn, a rotational unidirectional voltage between the brushes 65--65. Byproper design, said electromotive force may be used to assist the fieldwinding 24 in producing the total unidirectional-excitation of themachine 31.

The system of Fig. 11 is, in general, similar to that of Fig. 10 but theexciter machine 31 is rendered self-exciting, with respect to itsunidirectional component, by connecting the field winding 2 between thebrushes (E k-64 through a regulating resistor 27. The exciting systemmay be started by first causing the machine 31 to pick up as aselfexcited direct-current shunt machine as, for example, by opening aswitch 66. Said switch is then closed, connecting the exciter throughthe rotor circuit of the converter, whereupon it supplies bothalternating and direct current thereto. The field winding 2% has such ahigh resistance, as it is a shunt winding, that substantially noalternating fiux threads therethrough. The armature of the machine 31,however, carries both alter nating and direct current between thebrushes 6464:, and, therefore, has both types of fields along thehorizontal axes. Both alternating and direct rotational electromotivcforces are therefore induced between the brushes 65-65. The alternatingcomponent is transferred into the rotor circuit through the transformer36, whereas the unidirectional component serves merely to strengthen theunidirectional field in the vertical axis.

The system of Fig. is the same as Fig. 11 except that a neutralizingwinding 25 has been added to the machine 31, said winding being closedupon itself through an adjustable resistor 67. By this means, thealternating excitation may be adjusted, both in magnitude and in phase,thus rendering it possible to provide an alternating component of theexciting current that shall be out of phase with the rotor current ofthe converter. 7

It may, in some cases, be undesirable to use an exciter machine of thecommutator type and, under these conditions, I may employ analternating-current generator for the production of the desireddouble-frequency exciting current, as indicated in Fig.

13. The phase converter 14 carries, upon its shaft, the rotor 68 of analternating-current generator 69 having twice as many poles as thephase-converter l t.- The rotor field winding 18 of the rotor it isconnected through the armature coils 70-70 of the machine 69, said coilsbeing arranged in star. The rotor 68 carries the usual direct-current,field windings 71. 1' of an alternatingcurrent generator of the rotatingfield type, said field windings being energized from a source 72 throughsuitable slip rings 73. The source 72 constitutes a shunt-exciteddirect-current generator driven by a commutator motor 7%, the armatureof which is connected across the secondary winding 16 of the machine 1%.The motor 7 1 further comprises an exciting field winding 7 5 which isenergized in accordance with the load current by a suitable currenttransformer 76. The connections are such that an increase in loadproducesa decrease in the component of the field electromotive forcewhich is in line with the armature electromotive force, thus causing anincrease in the speed of the motor 75 with an increase in the load. Themotor 75 may further be provided with 'a .short-circuited inducingwinding 77. A directurrent component for chase correction may beinserted in the connection to one phase of the rotor circuit 18, asindicated at 78.

iVith the system arranged as above described, the fact tln t the excitermachine 69 has twice as many poles as the phase-converter le produces adouble-frequency exciting current, as is desirable for compounding. Byvirtue of the supply connections shown, the speed of said excitingmachine varies with the load, thus still further enlianciiigtliecompounding effect.

in all oft-he herein-described systems, it will be recognized that thedirect and alterhating exciting currents combine, as actually suppliedto the phase-converter, to form a single exciting current ofpulsating'or unsymmetrical alternating form.

While I have shown my invention in a plurality of forms, it will beobvious to those skilled in the art that it is susceptible of'variousminor changes and modifications without departing from the spiritthereof and I desire, therefore, that only such limitations shallbeplaced thereupon as are imposed by the prior artfor as are set forthin the appended claims.

j I claim as my invention:

1. The combination with a phase-converter of the rotary type, ofcooperating means for 'conductively supplying both direct andalternating currents to asecondary winding thereof.

2. The combination With a source of alternating current, of aphase-converter of the rotary type, and cooperating meansfor'conductively supplying both direct current and alternating currentof twice the frequency of said source to a secondary winding of saidconverter.

8. The combination with a phase-converter of the rotary type providedwith a wound secondary member, of a source of pulsating current, andconnections from said source to a winding of said secondary memher.

4. The combination with a phase-converter of the rotary type providedwith a wound secondary member, of an auxiliary dynamo-electric machine,driving means therefor, connections from the terminals thereof to asecondary Winding of said converter, and means for simultaneouslyproducing unidirectional and alternating exciting fields in saidauxiliary machine.

5. The combination with a source of alternating current, of aphase-converter provided with a wound secondary member connectedthereto, and means for supplying pulsating current to a winding of saidsecondary member, the frequency of pulsations thereof beingsubstantially twice the frequency of said source. 7

6. The combination with a source of alternating current, of aphase-converter of the rotary type connected thereto, an auxiliarydynamo-electric machine, driving means therefor, connections from theterminals of said auxiliary machine to a secondary winding of saidconverter, means for producing a unidirectional exciting flux in saidauxiliary machine, and means for simultaneously producing an alternatingexciting flux in said auxiliary machine of substantially twice thefrequency of said source of alternating current. i

In testimony whereof, I have hereunto subscribed my name this 21st dayof July,

RUDOLF E. HELLMUN D.

